1. Field of the Invention
The invention relates to the field of generating single wall magnetic domains.
2. Prior Art
Numerous single wall domain generators are well-known. These generators provide bubbles in response to an electrical signal, generally a pulse. Once a new bubble is generated it is moved along a propagation channel which originates adjacent to the generator. Domain generators generally fall into two categories. The first employs a seed domain which is split in what has been characterized as a "taffee-pulling operation" to generate additional domains. Examples of these generators are shown in U.S. Pat. Nos. 3,706,081; 3,706,082; and 3,781,833. In other generators, nucleation is employed to produce new domains through a magnetic field (U.S. Pat. No. 3,789,375) or through thermal nucleation (U.S. Pat. No. 3,786,452).
In magnetic bubble memories, a generator is employed to provide a stream of bubbles representing binary ones and zeros. This stream of bubbles is propagated in loops in a well-known manner to provide storage. These loops are arranged in a data storage block such as that shown in U.S. Pat. No. 3,838,407. A bubble generator is generally used along with reading circuitry for each data storage block. To increase the data rate of a bubble memory, a plurality of these blocks are used. However, this requires a plurality of bubble generators, one for each block, and an equal number of pulse generators to provide the electrical pulses for each of the bubble generators.
In the practical realization of bubble memory systems, a plurality of separate integrated circuit packages, which include a controller, pulse generators, read sensors and other circuits, are mounted on a printed circuit board along with the bubble memory. Numerous leads must interconnect the bubble memory with these other circuits. Among the leads are those which provide the electrical pulses to the bubble generators. Where a bubble memory includes a plurality of data storage blocks, additional leads are required to furnish pulses for each of the generators associated with each of the storage blocks. Thus, for example, if four data blocks are included on a single bubble memory substrate, four lines (in addition to a return line) are required to deliver the pulses to these generators.
It is necessary, from practical considerations, to minimize the number of leads which must be coupled to the bubble memory in a bubble memory system. Specifically, reducing the requirement for pins on the package which contains the bubble memory is important for the realization of a commercial bubble memory system.
As will be seen, the present invention allows two independent streams of bubbles to be generated from a single pulse generator. Thus, for example, four data storage blocks on a single substrate require only two leads (in addition to a return lead) to generate four independent streams of bubbles. Also, since two bubble generators are operated from a single pulse generator, the number of pulse generators is reduced.